“Know thyself” preach the inscription on Temple of Apollo, this method is excellent to present the evolution, however this oracle was born from totally different reason, probably.

Imagine a huge microscope, you are the subject, if you increase the magnification step by step, level to level you can see a fantastic, complex, miniature world, it is your human body.

Easy to see without microscope, that human body is constructed by many different organ, their object to harmonize many millions function. According to our complex operating system, the organs are very different: function, structure, mechanism, etc. If we exam this variegation with microscope, we can see, all organs is built up by cells, billions of cells. The human body is composed by 5*10¹⁵ cells, thus the statement is evident: the cell is building block of life.

Try to realize this huge number, what is it mean this mathematic formula in reality. Maybe the architecture is the most expressive way to present it. A monumental egypt pyramid is built up about 5*10⁶ big blocks, now try to imagine, that one big block is not a single separated stone, but contain thousand bricks, each bricks contain thousand gravels, each gravels contain thousand grains of sand. If we summarize it, we can say, a pyramid is composed by 5*10¹⁵ grains of sand.

Besides, that these million times billion cells cooperate with each other and create a complete working organization and still one single cell is also a very complex and sophisticated unit. By biology definition, the cell is capable of self-sufficing metabolism process and replicate the genetic material.

We can analyze the structure and mechanism of this unit with microscope. Don't forget the pyramid model, in further we exam only one grain of sand!

A cell have genetic materials, we can find them in the cell nucleus and call them chromosomes. The chromosome is a very long linear DNA molecule. Each human cells include 23 pairs chromosomes, these summarize about 25000 genes, it means about 3 billions base pairs. DNA is an individual characteristic molecule, for example in one human person case, each cells contain same DNA, but it is different from any other persons, similarly as a fingerprint. Basically, number of base pairs and their variation ensure limitless possibility. Certainly, the DNA is also different by different species.

DNA has a double helix shape, like a twisted ladder, where base pairs are rungs.

There are 4 different bases A, C, G, T.

We can divide them two different groups by bonding (H-bond):

two bonds: A, T,

three bonds: C, G,

We also can divide them two different groups by structure:

smaller (single-ringed): C, T,

larger (double-ringed): A, G,

Based on stability (interlocking and geometry) AT, or reverse TA, or CG, or reverse GC can generate a rung.

The role of DNA is the transcription and storage of information. 20 different amino-acid construct all proteins in all organism on the Earth, therefore it's enough to code only these amino-acids. The nature use the bases (base pairs) for coding. During the protein synthesis (production) the DNA double-helix is “unzipped”, the rungs are split, three bases in row, in sequence, create a three-digit code (codon, triplet). One codon determine one amino acid and start the transcription, construct the organism. The four different bases (A, C, G, T) ensure 64 pieces three-digit codons for 20 amino-acids, therefore sometimes it is happen that various codon belongs to same amino-acid, for example, lysine amino-acid is coded with AAA and AAG codon also.

A part of DNA, one gene, is responsible for one protein. The DNA also code a switch for each gene, this switch activate the right gene in right time.

And what are the role of proteins, there are the main components in cell. One cell may contain ten-thousands proteins and proteins are active parts of each process.